Sixty of the 71 victims were men. Eight women died, as did three children, ages 2, 3 and 8.
“We are talking about human trafficking, homicide, even murder,” said Johann Fuchs, state prosecutor of Eisenstadt.
News of the deaths comes as Europe is struggling to deal with a record swell of migrants and refugees traveling by land and sea to find a better life or escape conflict at home in the Middle East and Africa.
United Nations officials have called on European officials to improve their efforts to resolve the growing humanitarian crisis, including dealing with human traffickers preying on refugees of the sort thought to be responsible for the deaths in Austria.
The truck was found Thursday, abandoned on the side of the A4 highway, which links Budapest in Hungary to the Austrian capital, Vienna. When police opened it, they found the bodies decomposing in the heat.
They found a Syrian travel document inside the truck.
“We must assume now that these are refugees,” said Hans Peter Doskozil, police director of Austria’s Burgenland region. “In concrete terms, it is possible this is a Syrian refugee group.”
Hungarian police said Friday they had arrested three Bulgarian citizens and an Afghan citizen in connection with the truck.
“We are likely looking at a Bulgarian-Hungarian people smuggling ring,” Fuchs said.
About 3,000 trucks pass through that area of the highway daily, and checking each one of them is almost impossible, authorities said. Most human smugglers use smaller cars, making the use of trucks unusual.
On Friday, Hungarian police said they arrested a Romanian man who flipped a van carrying 18 refugees. In Surrey, England, authorities said they arrested 27 people suspected of illegally entering the country found in a suspicious truck at a gas station. The driver was also arrested.
In addition to the deaths of refugees trying to cross into Europe by road, thousands are making the perilous journey by sea.
Some 300,000 people have crossed the Mediterranean Sea into Greece and Italy this year alone, according to the office of the United Nations High Commissioner for Refugees. More refugees and migrants arrived in Greece in July alone than did in all of 2014, the agency said.
So far this year, 2,373 people have died trying to reach Europe by sea, according to the International Organization for Migration. In all of 2014, 3,281 people died.
In just one incident this week, 54 people died trying to cross the Mediterranean, the Italian coast guard said.
Comprehensive response urged
On Tuesday, a spokeswoman for the United Nations High Commissioner for Human Rights said the agency was calling on European leaders to organize a collective response to the needs of migrants and refugees flooding the continent.
“All European countries and the EU must act together and help those countries whose capacities are already overstretched such as Greece, the former Yugoslav Republic of Macedonia and Serbia,” spokeswoman Melissa Fleming said. “This includes capacity support, and support for equitable redistribution of refugees and asylum seekers across” the European Union.
The deaths in Austria highlight the need for a better strategy, Austrian Interior Minister Johanna Mikl-Leitner said at a news conference Thursday.
“This horrible crime shows that we must get even tougher in the battle against people smuggling,” she said. “People smugglers are criminals and not well-minded helpers. They do not care about the well-being of the refugees, they care about profit.”